188 Rhodora [OCTOBER 
The small size, the low elevation, and the free exposure render 
it likely that the vegetation of Gull Island is now in its permanent 
form, and not likely to tend toward the forest type which in time, 
without interference by man, will probably dominate Penikese. 
CHANGES IN THE FLORA. 
Considerable changes in the flora have taken place since 1873. 
In that year Jordan listed 114 species of ferns and seed plants, of 
which 44 were not found in the present survey. Itis not possible to 
be sure of the exact number, since the more detailed knowledge of 
the present day has given a more precise definition of species, and it 
is likely that in a few cases the same plant has been called by one 
name in Jordan’s list and by another in the present paper. Although 
synonymy has been taken into account, the possibility still remains, 
for example, that Jordan's Cerastium viscosum is our C. vulgatum, 
Archangelica Gmelini may be Ligusticum scothicum, Lycopus europaeus, 
L. americanus; Polygonum Hydropiper, P. acre; Atriplex patula, A. 
hastata: Festuca ovina, F. rubra. Making all possible allowances 
for such corrections, it still remains obvious that many, perhaps 
two score, species present on the island fifty years ago have disap- 
peared, victims perhaps of the grazing that continued for many years. 
On the other hand, the present list contains 166 species, no less 
than 94 being new to the Penikese flora. The presence of such a large 
number and proportion (57%) of invaders indicates that ecologically 
the island is progressing rapidly, since it has not been free of sheep 
for more than a dozen years. The record of its further changes should 
be followed carefully by the botanists of this region as giving a clear 
picture, very definitely outlined, of vegetational succession in a 
circumscribed area. 
The largest group of introduced species (30) have seeds which are 
without special adaptation for dispersal. These, most of which would 
be classed as weeds, were probably introduced accidentally along 
with garden seeds or in hay or otherwise. Many of them are found 
in the neighborhood of the hospital garden. Another considerable 
block (20 species) has been introduced directly by man, and many 
of these seem in a fair way to become thoroughly established. Of 
the remaining species, fifteen have wind-borne seeds, thirteen are 
found in or near ponds and may have been brought in among mud on 
the feet of birds, eleven have berries or fruits which are adapted to 
dispersal by seed-eating birds, two are beach plants which may have 
